Novel vinylic hindered amine light stabilizers

ABSTRACT

Vinylic hindered amine light stabilizers as novel polylmerizable light stabilizers are disclosed and have the general formula (I):  
                 
 
     wherein:  
     R 1  is C 1 to C 8 : alkyl, alkoxy, alkyl phenyl, hydroxy alkyl (all linear and branched), ally, acyl, cycloalkyl (cyclopentyl, cyclohexyl or cumyl: linear and branched); R 2  is hydrogen and methyl, R 3  is vinyl, C 1 -C 4  vinyl alkyl [H 2 C═C(R 4 )C 1 -C 4 ]; R 4  is H, C 1 -C 4  alkyl and alkyl phenyl and R 5  is H, C 1 -C 4  alkyl, X is 0, NH, C 1 -C 8  alkyloxy and alkylamino: (linear or branched).

FIELD OF INVENTION

[0001] This invention relates to vinylic-derivatives of Hindered AmineLight Stabilizer (HALS) having general formula (I):

[0002] wherein:

[0003] R₁ is C₁ to C₈ alkyl, alkoxy, alkyl phenyl, hydroxy alkyl (alllinear and branched) allyl, acyl, cycloalkyl (cyclopentyl, cyclohexyl orcumyl: linear and branched); R₂ is hydrogen and methyl, R₃ is vinyl,C₁-C₄ vinyl alkyl [H₂C═C(R₄)C₁-C₄] R₄ is H, C₁-C₄ alkyl and alkyl phenyland R₅ is H, C₁-C₄ alkyl, X is O, NH, C₁-C₈ alkyloxy and alkylamino:(linear or branched) and the process for the synthesis thereof.

BACKGROUND OF INVENTION

[0004] Monomeric hindered amine light stabilizers are gaining much moreimportance to stabilize the polyolefins and dicne elastomers. Naturaland synthetic polymers in common use are susceptible to photo-oxidativedegradation upon exposure to natural and artificial weathering. Thedeterioration of these polymeric materials is mainly due to the UVportion of sunlight reaching the earth surface. The net result ofdegradation is the loss in the Molecular weight and macroscopic physicalproperties. Polyolefins and unsaturated synthetic elastomers, beinghighly sensitive to oxidation, require the addition of stabilizers toprovide protection during processing, storage and end-use. The lowMolecular weight stabilizers are easily lost from the polymer throughevaporation, migration and extraction but, the compatible and mobilestabilizers usually give the best protection, In order to avoid thisloss polymer-bound and polymeric stabilizers have been devised.Moreover, since the degradation of a polymer commences from the surfaceand slowly proceeds into the matrix of the polymeric substrate, thestabilizers are therefore expected to be most potent if they areconcentrated at the surface. Therefore, they should be anchoredcovalently to the polymer surface. Monomeric light stabilizers thusprove to be the best choice to attain the desired photostability.

[0005] A discrete literature on the synthesis of the vinylic derivativesof HALS is available; some of these methods arc quite trivial and employcomplex routes using expensive reagents. Following patents andliterature: DE 2950067 (January 1981); DE 2642446 (March 1978); F. E.Karrer, Markromol. Chem. 181, 595 (German) 1980, N. S. Prostakov, A. V.Varlomov and G. A. Vasilev, Khim., Geterolsikl. Soedin., 6, 787(Russian) 1977, JP 53015385 (February 1978); D. V. Sokolov, M. N.Akirnova, K. D. Praliev, V. M. Kurilenko, Zh. N. Khlienko and K. M.Moiseeva, Khim.-Farm. Zh. 11, 47 (Russian) 1977; P. Hrdlovic and S.Chmela, Int. J. Polym. Mater., 13, 245 (1990); J. Pan, Z. Yang, L. Tong,W. Lau, W. Y. Wayne and C. S. Lee, Polym. Degrad. Stab. 44, 85, 1994;disclose the preparation and the mechanism of application of HALSderivatives.

[0006] Some of the authors have reported vinylic derivatives of HALS aspolymerizable light stabilizers wherein, the vinyl group is attached tothe hindered nitrogen atom. One of the vinylic derivative of HALS havingformula

[0007] is disclosed in the patent EP 24999145 A1 (December 1987). UponUV irradiation under atmospheric condition; the hindered nitrogenbearing the vinyl group gets converted into nitroxyl radical (N—O*).

[0008] As a result of which the hindered amine moiety gets detached fromthe covalently bonded vinyl group attached to the surface and is thusprone to be lost due to leaching/extraction/evaporation (shown in theScheme 1), making it inefficient. The objective of the present inventionis therefore, to provide a process for the preparation of novel vinylicHALS, which can the firmly bound to the polymer surface. Moreover, thisclass of monomeric HALS are known to be compatible with polyolefins,polystyrene and diene elastomers and can even be co-polymerized in adesired proportion to obtain ‘in chain’ and ‘chain end’ radicalscavengers.

DESCRIPTION OF THE INVENTION

[0009] Accordingly the present invention provides novel vinylic HinderedAmine Light Stabilizers derivative having general formula (I):

[0010] R₁ is C₁ to C₈ alkyl, alkoxy, alkyl phenyl, hydroxy alkyl (alllinear and branched), allyl, acyl, cycloalkyl (cyclopentyl, cyclohexylor cumyl: linear and branched); R₂ is hydrogen and methyl, R₃ is vinyl,C₁-C₄ vinyl alkyl [H₂C═C(R₄)C₁-C₄], R₄ is H, C₁-C₄ alkyl and alkylphenyl and R₅ is H, C₁-C₄ alkyl, X is O, NH, C₁-C₈ alkyloxy andalkylamino: (linear or branched).

[0011] In one of the other embodiments of the present invention thecarbonyl compound having formula (III) used to react with compoundhaving formula (II) is selected from formalin, formaldehyde,acetaldehyde, benzaldehyde, methyl ethyl ketone, methyl benzyl ketone,cyclohexyl methyl ketone.

[0012] In yet another embodiments of the present invention, the organicsolvent used for extracting the products is selected from the groupconsisting of diethyl ether, dichloromethane, ethyl acetate benzene.

[0013] In another embodiment the catalyst used, is selected from thegroup consisting of alkyl substituted amino pyridines exemplified byN,N-dimethyl-4-aminopyridine (DMAP), 4-amino pyridine and2-mercaptobenzoxazole.

[0014] In yet another embodiment the dry organic solvent used todissolve the catalyst and compound (IV) is selected from the groupconsisting of dichloromethane, dichloroethane, carbon tetrachloride,cyclohexane, n-hexane and dichloromethane, dichloroethane, carbontetrachloride, cyclohexane, n-hexane and chlorobenzene.

[0015] In still another embodiment the base used is selected fromaliphatic and aromatic substituted amine selected from the groupconsisting of triethyl amine, trimethyl amine 2,6-lutidine and pyridine.

[0016] In another embodiment the compound (V) added to react withcompound (IV) is selected from the group consisting of acryloylchloride, methacryloyl chloride, pentenoyl chloride and 3-butenoylchloride-3-phenyl.

[0017] In yet another embodiment the inert gas used is selected fromNitrogen and Argon.

[0018] In yet another embodiment the inorganic base used to neutralizethe solvent fraction containing the product is selected from the groupconsisting of sodium carbonate and pottassium sodium bicarbonate,potassium carbonate.

[0019] HALS monomers and some of its derivatives may be prepared by anyof the methods known in the art including those disclosed in Patents No.JP 53015385 28 (July 1978), Swiss CH 610898 (May 15, 1979), Swiss CH605927 (October 1978), Brit. GB 1492494 (November 1977) and Literature:T. Tsuchiya and H. Sashida, Heterocycles, 14, 1925-8 (1980). All thesepatents are incorporated herein by reference. HALS namely2,2,6,6-tetramethyl piperidine and 2,2,6,6-tetramethyl4-piperidinol maybe prepared by synthetic route disclosed by W. B. Lutz, S. Lazams and R.I. Meltzer, J. Org. Chem., 14, 530 (1949). All these patents andliterature are incorporated herein by reference.

[0020] The present invention is described herein below with referencesto examples which are illustrative only and should not be construed tolimit the scope of the present invention in any manner whatsoever.

EXAMPLE 1 Synthesis of 1,2,2,6,6-pentamethyl-4-piperidinol

[0021] 1,2,2,6,6-pentamethyl-4-piperidinol was synthesized uponreductive-amination of 2,2,6,6-tetramethyl-4-piperidinol. A mixture of2,2,6,6-tetramethyl-4-piperidinol (3.55 g, 0.02 M), 37% formalin (3.3mL) and 1 mL formic acid was heated under a reflux condensor on thesteam bath for 5 h. The reaction mixture was made basic with (1.0 M)potassium hydroxide solution and the product was extracted with ether(5×50 mL). The combined extract was washed with saturated solution ofpotassium carbonate (2×20 mL) and dried over anhydrous magnesium sulfateand finally the solvent was evaporated under vacuum. The residue wasthen sublimed at 0.05 mm, bath temperature 85° C. The white sublimateweighed 3.5 g to give 91% yield, mp=72-74° C.

EXAMPLE 2 Synthesis of 1,2,2,6,6-pentamethyl piperidinyl-4-acrylate

[0022] This model compound was synthesized strictly under dry and inertreaction conditions. 1,2,2,6,6-pentamethyl-4-piperidinol (1.0 g, 0.00588M) was taken in a two necked 25 mL capacity round bottom flask (RB)along with 4-dimethyl aminopyridine (DMAP) (30 mg, 0.245 mM) and waskept under nitrogen atomsphere. Dry dichloromethane (15 mL) was injectedinto the tightly closed RB through the rubber septum, followed by drytriethyl amine (TEA) (1.2 mL, 0.0087 M). This reaction mixture wasstirred for 10 minutes at room temperature followed by the addition ofacryloyl chloride (0.55 mL, 0.0069 M) with stirring. The reactionmixture was agitated at room temperature for 10 hrs. This reactionmixture was then quenched in ice water, and the product was extracted indichloromethane (4×25 mL). The combined extract was given (2×20 mL)washes of saturated sodium bicarbonate solution and finally dried overanhydrous magnesium sulfate. The solvent was evaporated under vacuum at38° C. over a rotavapor. The product was found to be almost pure (97.8%by Gas Chromatography). The TLC didn't show any spot of either thestarting material or the catalyst (DMAP). The 1,2,2,6,6-pentamethypiperidinyl-4-acrylate yield was 1.11 g (85%).

EXAMPLE 3 Synthesis of 1,2,2,6,6-pentamethyl piperidinyl-4-acrylamide

[0023] This compound was synthesized strictly under dry and inertreaction conditions. 1,2,2,6,6-pentamethy-4-aminopiperidine (1.0 g,0.00584 M) was taken in a two necked 25 mL capacity RB along with4-dimethyl aminopyridine (DMAP) (35 mg 0.28 mM) and was kept undernitrogen atmosphere. Dry dichloromethane (15 mL ) was injected into thetightly closed RB through the rubber septum, followed by dry triethylamine (TEA) (1.2 mL, 0.0087M). This reaction mixture was stirred for 10minutes at 10-12° C. followed by the gradual addition of acryloylchloride (0.55 mL 0.0069 M) with stirring at 0-5° C. The reactionmixture then, was allowed to stir at room temperature for approximately10 hrs. This reaction mixture was then quenched in ice water, and theproduct was extracted in dichloromethane (4×25 mL). The combined extractwas given (2×20 mL) washes of saturated potassium bicarbonate solutionand finally dried over anhydrous magnesium sulfate. The solvent wasevaporated under vacuum at 38° C. over a rotavapor. The crude productwas found to be 89.8% pure (by Gas Chromatography). It was furtherpurified by column chromatography. The yield of 1,2,2,4,4-pentamethypiperidinyl-4-acrylamide after purification was found to be 1.15 g(88%).

EXAMPLE 4 Synthesis of 1-tert-pentyl-2,2,6,6-tetramethylpiperidinyl-4-acrylate

[0024] 1-tert-pentyl-2,2,6,6-tetramethy-4-piperidinol was synthesizedstrictly under dry and inert reaction conditions.1-tert-pentyl-2,2,6,6-tetramethy-4-piperidinol (2.0 g, 0.00876 M) wastaken in a two necked 50 ml capacity round bottom flask (RB) along with4-dimethyl aminopyridine (DMAP) (53.5 mg, 0.437 mM) and was kept undernitrogen atmosphere. Dry dichloromethane (25 mL ) was injected into thetightly closed RB through the rubber septum, followed by dry triethylamine (TEA) (1.83 mL, 0.0131 M). This reaction mixture was stirred for10 minutes at room temperature followed by the addition of acryloylchloride (0.85 mL, 0.0105 M) with stirring. The reaction mixture wasagitated at room temperature for 10 hrs. This reaction mixture was thenquenched in ice water, and the product was extracted in dichloromethane(4×25 mL). The combined extract was given (2×20 mL,) washes of saturatedpotassium bicarbonate solution and finally dried over anhydrousmagnesium sulfate. The solvent was evaporated under vacuum at 38° C.over a rotavapor and the product was found to be almost pure. The TLCdidn't show any spot of either the starting material or the catalyst(DMAP). The yield of the product was 2.10 g (85%).

EXAMPLE 5 Synthesis of 1-allyl-2,2,6,6-tetramethylpiperidinyl-4-acrylate

[0025] 1-allyl-2,2,6,6-tetramethy-4-piperidinol (1.5 g, 0.00756 M) wastaken in a two necked 50 ml capacity round bottom flask (RB) along with4-dimethyl aminopyridine (DMAP) (46.2 mg, 0.387 mM) and was kept undernitrogen atmosphere. Dry n-hexane (25 mL) was injected into the tightlyclosed RB through the rubber septum, followed by dry triethyl amine(TEA) (1.73 mL, 0.0124 M). This reaction mixture was stirred for 10minutes at 10° C. followed by the addition of acryloyl chloride (0.79mL, 0.0098 M) with stirring at 0° C. The reaction mixture was agitatedinitially for 3 hrs at 5° C. and for the remaining period at roomtemperature for approximately 9 hrs under nitrogen atmosphere. Thisreaction mixture was then quenched in ice water, and the product wasextracted in n-hexane (4×25 mL). The combined extract was given (2×20mL) washes of saturated potassium bicarbonate solution and finally driedover anhydrous magnesium sulfate. The solvent was evaporated undervacuum at 38° C. over a rotavapor. The crude yield of1-allyl-2,2,6,6-tetramethy piperidinyl-4-acrylate was 1.65 g (86.5%).

EXAMPLE 6 Synthesis of 1-methylcylcohexyl-2,2,6,-tetramethylpiperidinyl-4-acrylate

[0026] This desired compound was synthesized strictly under dry andinert reaction conditions. 1-methylcylcohexyl-2,2,6,6-tetramethylpiperidinol (1.0 g, 0.00588 M) was taken in a two necked 25 ml capacityround bottom flask (RB) along with 4-dimethyl aminopyridine (DMAP) (30mg, 0.245 mM) and was kept under nitrogen atomsphere. Drydichloromethane (15 mL) was injected into the tightly closed RB throughthe rubber septum followed by dry triethyl amine (TEA) (1.2 mL, 0.0087M). This reaction mixture was stirred for 10 minutes at room temperaturefollowed by the addition of acryloyl chloride (0.55 mL, 0.0069 M) withstirring at 5° C. The reaction mixture was agitated at room temperaturefor 10 hrs. This reaction mixture was then quenched in ice water, andthe product was extracted in dichloromethane (4×25 mL). The combinedextract was given (2×20 mL) washes of saturated potassium bicarbonatesolution and finally dried over anhydrous magnesium sulfate. The solventwas evaporated under vacuum at 38° C. over a rotavapor. The product wasfound to be almost pure (97.8% by Gas Chromatography). The TLC didn'tshow any spot of either the starting material or the catalyst (DMAP).The yield of 1-methylcylcohexyl-2,2,6,6-tetramethylpiperidinyl-4-acrylate was found to be 1.003 g (82.8%),

EXAMPLE 7 Synthesis of 1-ethylphenyl-2,2,6,6-tetramethylpiperidinyl-4-acrylate

[0027] 1-ethylphenyl-2,2,6,6-tetramethyl-4-piperidinol (2.0 g, 0.0076 M)was taken in a two necked 50 mL capacity round bottom flask (RB) alongwith 4-dimethyl aminopyridine (DMAP) (46.5 mg, 0.387 mM) and was keptunder nitrogen atomsphere. Dry carbon tetrachloride (25 mL) was injectedinto the tightly closed RB through the rubber septum, followed by drypyridine (0.907 mL, 0.0112 M). This reaction mixture was stirred for 10minutes at 10-12° C. followed by the addition of acryloyl chloride (0.75mL, 0.0098 M) with stirring at 5° C. The reaction mixture was agitatedat room temperature for approximately 13 hrs. This reaction mixture wasthen quenched in ice water, and the product was extracted in ethylacetate (4×25 mL). The combined extract was given (2×20 mL) washes ofsaturated potassium bicarbonate solution and finally dried overanhydrous magnesium sulfate. The solvent was evaporated under vacuum at38° C. The yield of 1-ethylphenyl-2,2,6,6-tetramethylpiperidinyl-4-acrylate was 1.93 g (80%).

EXAMPLE 8 Synthesis of 1-methyl-2,6-dimethyl piperidinyl-4-acrylate

[0028] 1-methyl-2,6-diethyl-2,6-dimethyl-4-piperidinol; (2.5 g, 0.0125M) was taken in a two necked 50 mL capacity round bottom flask (RB)along with 4-dimethyl aminopyridine (DMAP) (76.5 mg, 0.625 mM) and waskept under nitrogen atmosphere. Dry dichloromethane (35 mL) was injectedinto the tightly closed RB through the rubber septum, followed by drytriethyl amine (TEA) (2.6 mL, 0.0187 M). This reaction mixture wasstirred for 10 minutes at room temperature followed by the addition ofacryloyl chloride (0.75 mL, 0.0098 M) with stirring at 5° C. Thereaction mixture was agitated at room temperature for 10 hrs. Thisreaction mixture was then quenched in ice water, and the product wasextracted in dichloromethane (4×25 mL). The combined extract was given(2×20 mL) washes of saturated potassium bicarbonate solution and finallydried over anhydrous magnesium sulfate. The solvent was evaporated undervacuum at 38° C. The 1-methyl-2,6-diethyl-2,6-dimethylpiperidinyl-4-acrylate was found to be almost pure and its yield was2.85 g (90%).

EXAMPLE 9 Synthesis 1-methyl-2,6-dimethyl piperidinyl--4-acrylamide

[0029] 1-methyl-2,6-diethyl-4aminopiperidine (2.0 g, 0,010 M) was takenin a two necked 50 mL capacity round bottom flask (RB) along with4-dimethyl aminopyridine (DMAP) (61.5 mg, 0.5 mM) and was kept undernitrogen atmosphere. Dry chlorobenzene (35 mL) was injected into thetightly closed RB through the rubber septum, followed by dry triethylamine (TEA) (1.96 mL, 0.0141 M). This reaction mixture was stirred for10 minutes at 15° C. followed by gradual addition of acryloyl chloride(0.75 mL, 0.0098 M) with stirring at 0-5° C. The reaction mixture wasinitially agitated at 5° C. for 3 hrs followed by stirring at roomtemperature for 10 hrs. This reaction mixture was then quenched in icewater, and the product was extracted in diethylether (4×25 mL). Thecombined extract was given (2×20 mL) washes of saturated potassiumbicarbonate solution and finally dried over anhydrous magnesium sulfate.The solvent was evaporated under vacuum at 38° C. over a rotavapor. Theproduct was found to be 85% pure and was further purified by columnchromatography under nitrogen atmosphere. The yield of the reaction was2.03 g (81%).

EXAMPLE 10 Synthesis of 1,2,2,4,6,6-hexamethyl piperidinyl-4-acrylate

[0030] 1,2,2,4,6,6-hexamethyl piperidinol (1.5 g, 0.0081 M) was taken ina two necked 50 mL capacity round bottom flask (RB) along with4-dimethyl aminopyridine (DMAP) (49.5 mg, 0.405 mM) and was kept undernitrogen atomsphere. Dry dichloromethane (30 mL) was injected into thetightly closed RB through the rubber septum, followed by dry triethylamine (TEA) (1.7 mL, 0.0121 M). This reaction mixture was stirred for 10minutes at room temperature followed by the addition of acryloylchloride (0.77 mL, 0.0097 M) with stirring at 5° C. The reaction mixturewas agitated at room temperature for 10 hrs. This reaction mixture wasthen quenched in ice water, and the product was extracted indichloromethane (4×25 mL). The combined extract was given (2×20 mL)washes of saturated potassium bicarbonate solution and finally driedover anhydrous magnesium sulfate. The solvent was evaporated undervacuum at 38° C. The product was found to be almost pure (98% pure byGC). 1,2,2,4,6,6-hexamethyl piperidinyl-4-acrylate obtained at the endof the reaction was 1.77 g ( (91.4%)

EXAMPLE 11 Synthesis of 1,2,2,4,6,6-hexamethyl peridinyl-4-acryamide

[0031] 1,2,2,4,6,6-hexamethyl-4-aminopiperidine (2.0 g, 0.0108 M) wastaken in a two necked 50 mL capacity round bottom flask (RB) along with4-dimethyl aminopyridine (DMAP) (66.5 mg, 0.543 mM) and was kept undernitrogen atomsphere. Dry dichloromethane (30 mL) was injected into thetightly closed RB through the rubber septum, followed by dry triethylamine (TEA) (2.1 mL, 0.015 M). This reaction mixture was stirred for 10minutes at 15° C. followed by the gradual addition of acryloyl chloride(0.86 mL, 0.01087 M) with stirring at 0-5° C. initially for 2 hrs. Thereaction mixture was then agitated at room temperature for 9 hrs. Thisreaction mixture was then quenched in ice water, and the product wasextracted in dichloromethane (4×25 mL). The combined extract was given(2×20 mL) washes potassium bicarbonate solution and finally dried overanhydrous magnesium sulfate. The solvent was evaporated at 38° C. undervacuum over rotavapor. The product was found to be almost pure (97.2%pure by GC). The yield of 1,2,2,4,6,6-hexamethyl peridinyl-4-acryamidewas 2.17 g (84%).

EXAMPLE 12 Synthesis of 1,2,2,6,6-pentamethyl piperidine-4-styrylacetate

[0032] 1,2,2,6,6-tetramethyl-4-piperidinol (2.5 g, 0.0145 M) was takenin a two necked 50 mL capacity round bottom flask (RB) along with4-dimethyl aminopyridine (DMAP) (88.5 mg 0.543 mM) and was kept undernitrogen atomsphere. Dry dichloromethane (30 mL) was injected into thetightly closed RB through the rubber septum, followed by dry triethylamine (TEA) (2.2 g, 0.0275 M). This reaction mixture was stilted for 20minutes at room temperature followed by the gradual addition of3-butenoyl chloride-3-phenyl (styrylacetyl chloride) (0.86 mL, 0.01087M) with stirring at 0° C. initially for 2 hrs. The reaction mixture wasthen agitated at room temperature for 9 hrs. This reaction mixture wasthen quenched in ice water, and the product was extracted indichloromethane (4×25 mL). The combined extract was given (2×20 mL)washes potassium bicarbonate solution and finally dried over anhydrousmagnesium sulfate. The solvent was evaporated at 38° C. under vacuumover rotavapor. The product was found to be almost pure (97.2% pure byGC). 1,2,2,6,6-pentamethyl piperidine-4-styrylacetate yielded at the endof the reaction was 3.85 g (81.5%).

1. Novel vinylic hindered amine light stabilizers of formula (I):

wherein: R₁ C₁ to C₈: alkyl, alkoxy, alkyl phenyl, hydroxy alkyl (alllinear and branched), allyl, acyl, cycloalkyl (cyclopentyl, cyclohexylor cumyl: linear and branched); R₂ is hydrogen and methyl, R₃ is vinyl,C₁-C₄ vinyl alkyl [H₂C═C (R₄)C₁-C₄], wherein R₄ is H, C₁-C₄ alkyl andalkyl phenyl and R₅ is H, C₁-C₄ alkyl, X is O, NH, C₁-C₈ alkyloxy andalkylamino: (linear or branched).